Corrosion prevention



eral formula:

United States Patent 2,840,526 n CORROSION PREVENTION '14 Claims. (Cl. 25258.55)

This invention relates to corrosion prevention, and in particular concerns compositions and methodsfor preventing corrosion in oil wells. 7

In many of the oiland gas-producing areas of the United States, the production of crude oil and gas is accompanied by the production of aqueous brines con- 20 taining dissolved carbon dioxide and/or hydrogen sulfide. Such brines are highly corrosive with respect to ferrous metals, and are responsible for frequent failures of metallic equipment associated with the well, e. g., the well tubing and easing, sucker rods and sucker rod boxes, pump parts, gathering lines, etc. In numerous instances the corrosion damage is so severe asto require replacement of sucker rods and pump parts as 'often as once a month and replacement of at least part of the tubing string as often as once a year. The cost of suchreplacement, together with the cost of constant inspection and the loss of production during the frequent periods when the well is shut down for inspection replacement of parts, is a major factor in the cost of the oil and/or gas produced. Among those who have been most closely associated with the problem of preventing corrosion inoil and gas wells it is generally conceded that the most satisfactory solution lies in the use of chemical corrosion inhibitors which can be. introduced directly into the well and admixed with the well fluids beforethe latter can come in contact with metallic well equipment. However, many of the materials which have been proposed for such use have not been satisfactory in actual practice, particularly where relatively high temperature conditions prevail (as in deep wells when the bottom hole temperature often exceeds 100 C.) and/or acidic gases such as carbon dioxide and/or hydrogen sulfide are present.

It is accordingly an object of the present invention to provide improved means. for preventing the corrosion of ferrous metals in oil and gas wells.

Another object is to provide means for preventing corrosion induced by.oil and/or. gas Swell brines in the presence of carbon dioxide and/or hydrogen sulfide at .the

elevated temperatures and pressures 'wliich-existwithin relatively deep wells.

A further object is to provide improved corrosion inhibitors for use in oil wells and the like.

Other and related objects will be apparent from the following detailed descriptionof the invention, and various advantages not specifically referred to hereinwill occur to those skilled in the art upon employment of the invention in practice.

I have now found that the above objects and attendant advantages may be realized through the provision and use of corrosion inhibiting compositions comprising as the essential active ingredient a reaction product of an ethylene polyamine and certain esters of unsaturated acids. More particularly, I have found that theproducts obtained by reacting an ethylene polyamine of the gen- Patented June 24, 1958 wherein x represents an integer from 1 to 5, with an alkyl ester of an unsaturated aliphatic carboxylic acid,

the alkyl groups of which contain from 4 to 22 carbon atoms, can be dissolved in dispersed in well fluids to 5 inhibit the corrosion thereby of ferrous metals to a remarkableextent under exceptionally adverse conditions I of temperature and pressure and in the presence of acidic gases such as carbon dioxide and hydrogen sulfide. The elfectiveness of these products against hydrogen sulfide corrosion is to some extent unique since many materials which are effective in the presence of carbon dioxide are substantially ineifective in the presence of hydrogen sulfide. The aforesaid reaction products are effective in very small amounts, and may be directly introduced into the well bore as such or, more preferably, in the form .of a solution of 10-90 percent concentration in a light petroleum hydrocarbon or other suitable ,solvent. As is hereinafter more fully explained, they may advantageously be employed in conjunction with dispersing agents adapted to promote their dispersion in both the aqueous and oil phases of the well efiluent. In addition to their corrosion inhibiting properties, the present products are surface active, andtheir presence in well efiluents promotes demulsification of the same.

The molecular structure of the present class of corrosion inhibitors can not accurately be defined. -The process by which they are made most probably involves a reaction wherein at least one of the amino groups of the ethylene polyamine adds to the ester at the-point of unsaturation: l

-- 'OH=OH++HN/ oHCH N but when the amine react'ant'contains both primary and secondary amino groups it is not known which is the more reactive," and it is hence not known at what point .the ester'molecule becomes attached to the ethylene 40 polyamine molecule. Very probably, the reaction product comprises a mixture of several individual compounds. 'Further'more,'in order toobtain the proper degree of oiland water-solubility, it is preferred that 'onlylbetween about 2 and about 4 moles of the unsaturated ester be combinedwitheach mole of the ethylene polyamine. Accordingly, when the number of amino groups in the ethylene polyamine exceeds the number of moles of unsaturated ester employed, the product willalmost of necessity comprise a mixture of compounds. 'For these reasons, the. members of the present class of corrosion inhibitors are herein referred to as reaction products rather than as definite chemical compounds. 7 s

The general formula of the ethylene polyamines employed inpreparing the present. corrosion inhibiting re- 5 action products has been previously given. The compounds embraced by such formula are ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene "pentamin'e and pentaethylene hexarnine' The compounds containing 3 or more amino groups are preferred.

The unsaturated esters employed in preparing the present corrosion inhibitors are alkyl esters of unsaturated aliphatidcarboxylic acids. The esterified'alkyl groups should contain from 4 to 22 carbon atoms, and the uns aturated acid may-be monobasic or diba'sic. As examples of such esters there may be mentioned n-hexyl acrylate, isohexyl methacrylate, di-(Z-ethylhexyl) male- -ate, tert.'-octyl crotonate, n-heptyl isocrotonate, lauryl tiglate, ce'tyl oleate, nonyl linoleate, eicosyl geranate, isobutyl'methacrylate, 2-ethylhexyl ricinoleate, 'di-(n-octyl) 7O fumarate, di-de'cyl citroconate, lauryl methacrylate, tetradecyl crotonate, nonyl acrylate, etc. Because of their general availability andrelativelylow cost, the alkyl esters of acrylic, methacrylic and maleic acids are pre-' ferred.

The reaction by which the present products are formed takes place spontaneously simply upon admixture of the two reactants, at room temperature. If desired, the reaction may be. accelerated by heat n b t fl? R c ion temperature should be maintained below about lQQQ. in order to avoid the formation of amides. In some cases it may be necessary to' provide means for cooling the re;- action mixture in order to avoid excessive reaction temperatures. Conveniently, the reaction is carried outin the presenceof an inert liquidreaction medium, e.1g., benzene, toluene, kerosene extract, etc., and, if desired, such liquid medium may be allowed to remain with the product to facilitate its handlingand 'applicationto corrosion inhibiting uses. The number of moles of ester employed per mole of ethylene polyamine should not exceed the number of amino groups in the latter, i. 'e., should not exceed x+1 moles, and is preferably between about 2 and about 4. This preference is based on the fact that the products which contain an average of more than 4 long chain alkyl ester groups in the molecule are too oil-soluble to become effectively distributed in the aqueous phase of well effluents without the used of added dispersing agents. Conversely, the products'which contain an average of less than 2 of such groups in the molecule are too water-soluble to become effectively distributed in the oil phase without the use of dispersing agents. From a corrosion inhibiting standpoint, however, the products containing an average of less than 2 or more than 4 of such groups in the molecule are highly satisfactory; they are less preferred only because a supplementary dispersing agent must be employed to secure best results.

The following examples will illustrate the preparation of several corrosion inhibitors of the present class, but are not to be construed as limiting the invention.

EXAMPLE I EXAMPLE II One mole of tetraethylene pentamine is dissolved in an equal volume of kerosene extract (B. R.=4 00600 'F.), and 2.5 moles of Z-ethylhexyl acrylate are added gradually with stirring while maintaining the reactiontemperature at about 40 C. The resulting dark brown liquid is suitable for use directly as a corrosion inhibitor.

EXAMPLE HI 7 Example II is repeated, substituting di-(Z-ethylhexyl) maleate for the 2-ethylhexyl acrylate.

EXAMPLE IV Example II is repeated, substituting triethylene tetramine for the tetraethylene pentamine.

EXAMPLE V Three moles of decyl crotonate are added gradually to one mole of diethylene triamine while maintaining the reaction temperature at about 80? C. The resulting product is a dark brown viscous liquid.

In treating a well to inhibit corrosion therein in accordance with one embodiment of the invention, one or a mixture of the above-described reaction products is simply introduced into the well bore yia the well tubing or casing in an amount suflicient to effect asubstantial degree of corrosion inhibition. Such amount will depend primarily upon the nature of the .well fluid and the temperatures and pressures prevailing-within the well, but

highly satisfactory results are usually obtained, even under exceptionally adverse conditions, when the volume of inhibitor in the well is maintained between about 0.0001 and about 0.01 percent of the volume of the fluid in the well. As previously stated, however, the inhibitors of the present class are usually more conveniently employed in the form of a solution in a suitable solvent, preferably a relatively light petroleum hydrocarbon.

When the reaction product contains an average of less than about 2 ormor e'than about-"4 ester groups in the molecule, it is'preferably employed in conjunction with one or more dispersing agents which may or may not have corrosion inhibiting properties of their own. The primary purpose of such agents is to promote uniform dispersion of the inhibitor in the well fluid, and since such fluod comprises both water or brine and oil, the dispersing agent may be either wateror oil-soluble, or both. A mixture of two or more types of dispensing agents may also be employed. A wide variety of both watersoluble and oil-soluble types isknown, and any of them may be employed in preparing corrosion inhibiting compositions comprising-one or more of the present class of reaction products as the essential active ingredient. Oilsoluble sulfonic acids, such as the petroleum sulfonic acids, and the salts thereof, and nonionic dispersing agents such as the Spans and Tweens and the 'fatty acid amides are preferred. Compositions of this type ordinarily comprise between about 5 and about 20 percent by Weight of the active ingredient and between aboutZ and about 10 percent "by weightof one or a mixture of dispersing agents, with the remainder consisting of an inert solvent.

"The composition may also contain scale inhibitors, such as the polyphosphates and scale-inhibiting acids, and if desired, dispersing agents may be employed even though the active ingredientis of the preferred type containing .between 2 and 4 ester groups in the molecule.

EXAMPLE VI .Pts. by wt.

Reaction product of 2 moles of heptyl methacrylate with 1 mole of ethylene diamine 10 Kerosene extract (B. R.=400-600 E); 90

EXAMPLE VII Reaction product of 4 moles of octyl crotonate with 1 mole of tetraethylene diamine 10 Kerosene extract (B. R.=400600 F.) Sodium petroleum sulfonate 8 Sorbitan tri-oleate 2 EXAMPLE VIII 7 Reaction product of 3 moles of lauryl methacrylate with 1 mole of diethylene triamine 20 ,Toluene 74 Sorbitan tri-nleate 2 Sodium tri-polyphosphate 4 EXAMPLE IX Reaction product of 1 mole of di-hexyl fumarate with 1 mole of ethylene diamine Benzene Sodium petroleum sulfonate 5 7 EXAMPLE X Reaction product of 5 moles of amyl acrylate with 1 mole of tetraethylene pentamine Kerosene extract p 80 .Reaction product of castor .oil fatty .acidswith diethanolamine 3 ,Sodium petrolenm sulfonate. 2

EXAMPLE XI Reaction product of 2.5 moles of octadecyl methacrylate with 1 mole of mixed polyethylene polyamines (Polyarnine H") 5O Kerosene extract 50 The appended table presents data illustrating the effectiveness of the present class of products as inhibitors of corrosion by hydrogen sulfide brine. These data were obtained by the following test procedure: A 1- liter Ehrlenmeyer flask is swept free of air with a stream of hydrogen sulfide, and is then filled with about 750 ml. of a simulated oil field brine which consists of 3% aqueous sodium chloride saturated with hydrogen sulfide. The material to be tested is dissolved in kerosene extract (B. R.=400-600 F.) to form a 17 weight per cent solution, and sufficient of such solution is added to the brine to provide a concentration of 50 p. p. m. of the test material. A weighed and polished steel test specimen is then suspended in the brine, and the flask is stoppered and held at about 25 C. for. 7 days. The test specimen is then removed, washed in distilled water, and reweighed. The efficiency of the inhibitor is calculated as follows:

Percent efiiciency=w 100 1 where W is the loss in specimen weight with an uninhibited brine and W is the loss in specimen weight with the inhibited brine.

While the principle of the invention has been described above as it is applied in the prevention of corrosion in well bores, it will be apparent that it is also applicable to corrosion prevention in pipelines, storage tanks, and other locations where corrosive effluents from oil or gas wells come in contact with ferrous metals.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the methods or materials employed, provided the steps or products stated by any of the following claims, or the equivalent of such stated steps or products, be employed or obtained.

I, therefore, particularly point out and distinctly claim as my invention:

1. The method for reducing the corrosiveness of oil and gas well fluids comprising moisture and at least one acidic material selected from the class consisting of carbon dioxide and hydrogen sulfide towards ferrous metals which comprises introducing into said well fluid a corrosion inhibiting amount of a product prepared by reacting an ethylene polyamine of the general formula wherein x represents an integer from 1 to 5, inclusive, with an alkyl ester of an unsaturated aliphatic carboxylic acid, the alkyl group of which contains from 4 to 22 carbon atoms, said reaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 6, but not more than x+l, moles of said alkyl ester being employed per mole of said ethylene polyamine.

2. The process of claim 1 wherein the said reaction product is introduced into the well fluid in the form of a solution in an organic solvent.

3. The process of claim 1 wherein the said ethylene polyamine is tetraethylene pentamine.

4. The process of claim 1 wherein the said alkyl ester of an unsaturated aliphatic carboxylic acid is an alkyl ester of an acid selected from the class consisting of acrylic, methacrylic and maleic acids.

5. The process of claim 1 wherein ethylene polyamine is tetraethylene pentamine and the said alkylester is 2- ethylhexyl acrylate.

6. The process of claim 1 wherein the said reaction product is introduced into the well fluid in an amount corresponding to between about 0.0001 and about 0.01 per cent by volume of the fluid.

7. The process of claim 1 wherein the said reaction product is introduced into the well fluid in the form of a solution comprising between about 10 and about percent by weight of said product and between about 90 and about 10 percent by weight of a liquid petroleum hydrocarbon solvent.

8. A corrosion inhibiting composition comprising (1) between about 10 and about 90 percent by weight of a product prepared by reacting an ethylene polyamine of the general formula wherein x represents an integer from l to 5, inclusive, with an alkyl ester of an unsaturated aliphatic carboxylic acid, the alkyl group of which contains from 6 to 22 carbon atoms, said reaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 6,

but not morethan x+1, moles of said ester being emconsisting of acrylic, methacrylic and maleic acids,

11. A composition as defined by claim 8 wherein the said ethylene polyamine is tetraethylene pentamine and the said ester is 2-ethylhexyl acrylate.

12. A corrosion inhibiting composition comprising (1) between about 10 and about 90 percent by weight of a product prepared by reacting an ethylene polyamine of the general formula NH CH H NH) ,,-H

wherein x represents an integer from 1 to 5, inclusive, with an alkyl ester of an unsaturated aliphatic carboxylic acid, the alkyl group of which contains from 6 to 22 carbon atoms, said reaction being carried out at a temperature below that at which any substantial amounts of amides are formed and between about 1 and about 6, but more than x+1, moles of said ester being employed per mole of said ethylene polyamine, (2) between about 2 and about 10 percent by weight of an organic dispersing agent, and (3) suificient of a liquid petroleum hydrocarbon to make percent by weight.

13. A composition as defined by claim 12 wherein the said alkyl ester of an unsaturated aliphatic carboxylic acid is an alkyl ester of an acid selected from the class consisting of acrylic, methacrylic and maleic acids.

14. A composition as defined by claim 12 wherein the said ethylene polyamine is tetraethylene pentamine and said ester is 2-ethylhexyl acrylate;

References Cited in the file of this patent UNITED STATES PATENTS 2,532,391 Bersworth Dec. 5, 1950 2,680,094 Bartlett et al. June 1, 1954 2,756,211 Jones July 24, 1956 2,763,612 Raifsnider et al. Sept. 18, 1956 UNITED STATES PATENT oFFIcE QERTIFIQATE 0F CORRECTIQN Patent Non z sropze June 24 195 Howard Fa Keller Jr It is hereby certified that error appears in the printed specificati of the above numbered patent requiring correction and that the said Lette Patent should read as corrected below.

Column 4,, line 17, for "fluod" read fluid line l9, for "dispensing" read dispersing column 6, line 38, after the claim number "10" strike out'the comma and. insert instead a period; line 41, after "acids" strike out the comma and insert instead a period; same column, line 49 the chemical equation should appear as shown below inste of as in the patent:

is us m n mn a same column 6 line 57, aftsr "but" insert snot Signed and sealed this 16th day of September 1958,

KARL AXLINE ROEERT c. WATSO Commissioner of Pate Attesting Ofl'icer UNITED STATES PATENT OFFICE CE TEFECATE 0F CORRECTEQN Patent No., 2,840,526

June" 24, 1958 Howard .Fo Keller Jra It is hereby certified that error appears in the printed specificatio of the above numbered patent requiring correction and that the said Letter Patent should read as corrected below.

Colmnn 4,1 line 17, for "fluod" read fluid line 1% for "dispensing" read e dispersing column 6, line 38, after the claim number "10" strike out the eomma and insert instead a. period; line 41, after acids" strike out the some and insert instead a period; same column, line 4% the chemical equation should appear as shown below instead of as in the patent:

at 6 2H -H I same column 6, line 57 after "but" insert r not w Signed and sealed this 16th day of September 1958,,

gSEAL) ttest:

KARL HO XLTAE ROBERT c. WATSON Commissioner of Patent Attesting Officer 

1. THE METHOD FOR REDUCING THE CORROSIVENESS OF OIL AND GAS WELL FLUIDS COMPRISING MOISTURE AND AT LEAST ONE ACIDIC MATERIAL SELECTED FROM THE CLASS CONSISTING OF CARBON DIOXIDE AND HYDROGEN SULFIDE TOWARDS FERROUS METALS WHICH COMPRISES INTRODUCING INTO SAID WELL FLUID A CORROSION INHIBITING AMOUNT OF A PRODUCT PREPARED BY REACTING AN ETHYLENE POLYAMINE OF THE GENERAL FORMULA 